Sulfonated silica-based cation-exchange nanofiber membranes with superior self-cleaning abilities for electrochemical water treatment applications

Electrochemical treatments in (waste)water management show high potential in the global water resource crisis, but are often limited by the ion-exchange membrane (IEM) performance. Low chemical resistance and fouling are major issues in the development of next-generation IEMs. Sulfonated silica-based nanofiber cation-exchange membranes (CEMs) offer a promising solution to these issues due to their superior chemical resistance and self-cleaning properties. Via the direct electrospinning of a sol-gel solution starting from tetraethyl orthosilicate (TEOS) and 3-mercaptopropyl triethoxysilane (MPTES), nanofiber membranes with an ion-exchange capacity (IEC) of 1.3 mmol g(-1) can be produced without the need of an additional matrix. The produced nanofiber CEM performs excellent in lab-scale electrochemical tests, with a resistance of 3.2 +/- 0.4 *10-3 Omega m(2) and a Coulombic efficiency of +/- 70 % for the transport of Na+ using a current density of either 128 or 256 A/m(-2). Furthermore, the nanofiber CEM shows outstanding resistance against strong acidic solutions and chlorine. After fouling of the membrane with CaCO3, the nanofiber CEM shows self-cleaning properties, eliminating the need for an additional cleaning step during usage. These results illustrate the excellent performance of the silica -based nanofiber CEM for industrial water treatment applications.